Method for manufacturing flexible display device and flexible display device

ABSTRACT

A flexible display device and a method for manufacturing a flexible display are provided. The flexible display device includes a flexible substrate, a display element layer formed on the flexible substrate; an insulating protective layer covering the display element layer; and a rigid substrate. The rigid substrate has an etching selectivity at least 20 times greater than that of the insulating protective layer.

This application claims the benefit of Korean Patent Application No.10-2006-117867 filed in Korea on Nov. 27, 2006, which is herebyincorporated by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method for manufacturing a flexibledisplay device and a flexible display device thereby, and moreparticularly, to a method for manufacturing a flexible display device inwhich the stability of the process is enhanced and the production yieldis increased.

2. Description of the Related Art

In the display device market, the flat panel display (hereinafter “FPD”)has been remarkably rapidly replacing the CRT (cathode ray tube)monitor. There are many kinds of FDP devices, for example, the liquidcrystal display (LCD), the plasma display panel (PDP) and the organicelectro-luminescence display (OELD). An FPD has lighter weight andthinner thickness as compared with a CRT. Therefore, an FPD isparticularly suitable for a large size display system or a portabledisplay system. Because the main elements of the FPD are formed by hightemperature processes, most FPD uses glass substrates to endure againstthe high temperature required in the manufacturing processes. However,because the glass substrate is rigid at room temperature, the glasssubstrate cannot be freely applied to a flexible display device.Recently, flexible materials have been used for the FPD to developflexible display devices such that the displays can be rolled or foldedto be freely handled in any conditions. That is, using a flexiblematerial such as plastic film or metal foil, a flexible display willhave the same display performance even when it is rolled or bent and,therefore, are of great interest in the display industries.

The currently used flexible substrate materials such as plasticsubstrates or metal foils have the heat resistances inferior to those ofglass substrates. Therefore, these flexible substrates can be easilydeformed by the high temperatures applied during the processing stepsfor manufacturing the display elements. The deformed substrate cannotguarantee the quality of the display elements formed thereon. That is,it is impossible to form the display elements on the flexible substratedirectly.

Recently, to overcome the above problem, the substrate transcriptionmethod has been suggested. After forming the display elements on a rigidsubstrate, such as a glass substrate, a flexible substrate is attachedto the display elements, and then, the glass (rigid) substrate isremoved.

The FIGS. 1A to 1D illustrate a method for manufacturing the flexibledisplay device according to the substrate transcription method accordingto the related art. The substrate transcription method includes formingan insulating protection layer 3 on a glass substrate 1, forming adisplay element layer 5, attaching a flexible substrate 7, and removingthe glass substrate 1 and the insulating protection layer 3.

In the step of forming the insulating protection layer 3, as shown inFIG. 1A, the insulating protection layer 3 is deposited on a glasssubstrate 1 with a thickness to have enough thermal resistance againstthe heat of the manufacturing process. The insulating protection layer 3is made of a silicon oxide (SiOx) or a silicon nitride (SiNx).

In the step for forming the display element layer 5, as shown in FIG.1B, various elements (lines, electrodes, thin film transistors, etc)configuring the display elements are formed on the insulating protectionlayer 3. The step for forming the display element layer 5 includes manyphoto-lithography processes and etching processes.

In the step for attaching the flexible substrate 7, as shown in FIG. 1C,the flexible substrate 7, such as a thin plastic substrate or a metalfoil, is attached on the display element layer 5 by an adhesive. Theflexible substrate 7 will be the actual substrate of the display deviceto support the display element layer 5 while permitting flexibility ofthe display device.

Finally in the step of removing the glass substrate 1 and the insulatingprotection layer 3, as shown in FIG. 1D, the glass substrate 1 and theinsulating protection layer 3 are removed using an etchant, such ashydrogen fluoride (HF). Further, a polishing method using a grinder,such as alumina, is used after etching the glass substrate 1 forenhancing the etched surface. The polishing method for removing theglass substrate 1 cannot be applied when the size (diagonal length) ofthe glass substrate 1 is larger than 1 m. When removing the glasssubstrate 1 having a diagonal length over 1 m, the etching process isonly used. Because only the flexible substrate 7 remains on the displayelement layer 5, the display device is flexible.

As mentioned above, when the etching process is applied to the substratetranscription method, the etchant may intrude into and attack thedisplay element layer 5 while the insulating protection layer 3 isremoved. As a result, the stability of the production process and theproduction yield of the flexible display device are degraded.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a method formanufacturing the flexible display device and a flexible display devicethat substantially obviates one or more of the problems due tolimitations and disadvantages of the related art.

An object of the present invention is to provide a method formanufacturing a flexible display device where production stability isensured.

Another objection of the present invention is to provide a method formanufacturing a flexible display device manufacturing method withenhanced production yield.

Additional features and advantages of the invention will be set forth inthe description which follows, and in part will be apparent from thedescription, or may be learned by practice of the invention. Theobjectives and other advantages of the invention will be realized andattained by the structure particularly pointed out in the writtendescription and claims hereof as well as the appended drawings.

To achieve these and other advantages and in accordance with the purposeof the present invention, as embodied and broadly described, a flexibledisplay device comprises a flexible substrate; a display element layerformed on the flexible substrate; an insulating protective layercovering the display element layer; and a rigid substrate having anetching selectivity at least 20 times greater than that of theinsulating protective layer.

In another aspect, a manufacturing method for flexible display devicecomprises the steps of forming an insulating protection layer on a firstsubstrate; forming a display element layer on the insulating protectionlayer; attaching a flexible substrate on the display element layer; andetching the first substrate to remove the first substrate using anetchant having a selective etching ratio of the insulating protectionlayer to the first substrate of less than 1/20.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory and areintended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a furtherunderstanding of the invention and are incorporated in and constitute apart of this specification, illustrate embodiments of the invention andtogether with the description serve to explain the principles of theinvention. In the drawings:

FIGS. 1A to 1D illustrate a method for manufacturing a flexible displaydevice step-by-step using the substrate transcription method accordingto the related art;

FIG. 2 illustrates a structure of a flexible display device according toa first exemplary embodiment of the present invention;

FIGS. 3A to 3D illustrate a method for manufacturing a flexible displaydevice step-by-step according to the first exemplary embodiment of thepresent invention;

FIGS. 4A and 4B illustrate a method for etching the glass substrateaccording to an exemplary embodiment of the present invention;

FIGS. 5A and 5B illustrate methods for forming and removing a resinbarrier shown in the FIGS. 4A and 4B according to exemplary embodimentof the present invention;

FIG. 6 illustrates a flexible display device according to a secondexemplary embodiment of the present invention;

FIG. 7 illustrates an example of a flexible display device having a TFTin detail according to the present invention; and

FIGS. 8A to 8E illustrate a method for manufacturing a flexible displaydevice step-by-step according to a third embodiment of the presentinvention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made in detail to the preferred embodiments of thepresent invention, examples of which are illustrated in the accompanyingdrawings. The present invention will now be described with reference toFIG. 2 through FIG. 8.

In the method for manufacturing a flexible display device and thestructure of a flexible display device according to the presentinvention, the insulating protection layer exists at the final structureof the flexible display device. To protect the display devices from theetchant in the process for etching the rigid substrate, thereby removingit from the final flexible display device, the insulating protectionlayer is not removed during the manufacturing process. Thus, theinsulating protection layer remains in the final product.

The flexible display device according to the first exemplary embodimentof the present invention, as shown in FIG. 2, includes a flexiblesubstrate 27, a display element layer 25 on the flexible substrate 27and an insulating protection layer 23 formed on the display elementlayer 25. Further, the insulating protection layer 23 may comprise amultiple layer structure.

As shown in FIGS. 3A to 3D, the method for manufacturing the flexibledisplay device according to the first exemplary embodiment of thepresent invention includes steps of forming an insulating protectionlayer 23 on a glass substrate 21, forming a display element layer 25,attaching a flexible substrate 27 and removing the glass substrate 21.As shown in FIG. 3A, in the first step of the method for manufacturing aflexible display device according to the first exemplary embodiment, aninsulating protection layer 23 is deposited on one side of a glasssubstrate 21, a rigid substrate. The insulating protection layer 23includes a silicon layer or a metal oxide layer, such as chrome oxide(Cr_(x)O_(y)), tantalum oxide (Ta_(x)O_(y)) or aluminum oxide(Al_(x)O_(y)). When the silicon layer is used for the insulatingprotection layer 23, it is deposited on the glass substrate 27 using aPECVD method. When the metal oxide layer is used for the insulatingprotection layer 23, a metal layer is deposited by the sputteringmethod, and then, the metal layer is oxidized using an O₂ plasma or theanodizing method.

As shown in FIG. 3B, in the second step of the method according to thefirst exemplary embodiment, a display element layer 25 is formed on theinsulating protection layer 25. The display element layer 25 includesvarious elements for operating the display device. For example, if theflexible display device is for a TFT LCD device, the display elementlayer 25 can include a TFT array, gate lines and data lines. If theflexible display device is for an OELD device, the display element layer25 can include an organic diode array.

As shown in FIG. 3C, in the third step of the method according to thefirst exemplary embodiment, a flexible substrate 27 is attached on thedisplay element layer 25 with an acrylic adhesive including chloroform.The flexible substrate 27 will be the actual substrate of the displaydevice to support the display element layer 25 while permittingflexibility of the display device.

As shown in FIG. 3D, in the fourth step of the method according to thefirst exemplary embodiment, the glass substrate 21 is removed by anetching process, such as wet etching or dry etching. For wet etching,the etchant includes buttered hydrogen fluoride (HF+NH₄F:BHF). For dryetching, the etchant includes CF₄+O₂ or SF₆+O₂.

In the process for etching the glass substrate 21, the processing timeincludes the etch time, the theoretical time required to completelyremove the glass substrate 21, and the over etch time in addition to theetch time. The over etch time is determined in consideration thatunetched parts remain after the etch time, thereby ensuring theuniformity of the etched surface. The insulating protection layer 23protects the display element layer 25 during the etching process. Thatis, the insulating protection layer 23, in an exemplary situation,should not be etched in the step for removing the glass substrate 21. Asa result, in this exemplary method for manufacturing the flexibledisplay device according to the present invention, the etching ratio ofthe glass substrate 21 to the insulating protection layer 23 is 20:1 orhigher (for example 30:1 or 40:1). Thus, the insulating protection layer23 is etched with unit amount of 1 while the glass substrate is etchedwith amount of 20 units at the same time. This is, for the insulatingprotection layer 23 is not etched when the glass substrate 21 is etchedout in the over etch time. The etch ratio can be varied according to thethickness of the glass substrate 21. The ratio of 20:1 is determined byconsidering that the thickness of currently used glass substrate 21 isin range of 200 μm-700 μm. In the first exemplary embodiment, theetching selectivity of the silicon layer to the glass is 1/20 or less.That is, the etching ratio of the glass to the silicon layer is 20:1 orhigher. Therefore, the silicon layer is not etched during the over etchtime of the etching process.

When the insulating protection layer 23 is deposited thicker, it wouldnot be removed during the over etch time. However, it may be restrictedto be under certain thickness. The reason for restricting the thicknessof the insulating protection layer 23 is that the glass substrate 21 hasa stress from the deposited insulating protection layer 23.Specifically, the glass substrate 21 is hardly deformed by the heatbecause it has a high thermal expansion coefficient. However, theinsulating protection layer 23 having a low thermal expansioncoefficient is easily shrunken after being deposited on the glasssubstrate 21. Therefore, when the insulating protection layer 23 isdeposited in thick on the glass substrate, the glass substrate 21 isaffected by the stress from the shrinkage of the insulating protectionlayer 23. This stress from the insulating protection layer 23 isproportional to its thickness. So that, the glass substrate 21 may becracked or broken. As a result, the display element layer 25 on theglass substrate 21 may be damaged. Therefore, it is preferable to setthe thickness of the insulating protection layer 23 to be less than 1μm.

After removing the glass substrate 21, turning over the final product,then the flexible display device as shown in FIG. 2 can be completed.

FIGS. 4A and 4B explain the method for etching the glass substrate.After attaching the flexible substrate 27 on the display element layer25, the display structure may be soaked into a bath filled with anetchant. By dipping the whole display device into an etchant, thedisplay element layer 25 may be damaged by the etchant through thelateral side. To overcome this problem, in an exemplary technique of thepresent invention, turning over the display device after attaching theflexible substrate 27 as shown in FIG. 4A, a resin barrier 41 is formedon the edge of the other side of the glass substrate 21. Within theresin barrier 41, an etchant 42 is filled by the VALC method aftercalculating a required etchant amount for removing the glass substrate21. After removing the glass substrate 21 using the etchant, the resinbarrier is removed by cutting the display device along the cutting line45. The cutting line 45 is disposed between the resin barrier 41 and theeffective region (A1) of the display device. The effective region (A1)is the area in which the elements of the display device are formed.

In the step of etching the glass substrate 21, the etchant may attackthe glass substrate 21 under the resin barrier 41 so that the under-cutmay be formed as shown in FIG. 4B. When the width (w) of the resinbarrier 41 is equal to or less than the thickness (t) of the glasssubstrate 21, the resin barrier 41 may be cut out by this under cutphenomena. In that case, the etchant may attack the display elementlayer 25 at this portion. Therefore, to stably complete the etchingprocess, the width of the resin barrier 41 should be thicker than thethickness of the glass substrate 21.

FIGS. 5A and 5B explain the pattern of the resin barrier 41 of FIGS. 4Aand 4B and the method for removing the resin barrier 41. In theeffective region (A1) of the display device, many units of display panel(Bmn: m and n are positive integer numbers) are disposed in a matrixarray. The unit display panels (Bmn) are separated with a certaindistance between them.

For one example for pattern of resin barrier 41, the resin barrier 41 isformed at the four edge side edges of the glass substrate 21 to surroundall unit display panels (Bmn) as shown in FIG. 5A. In that case, thecutting line 45 for removing the resin barrier 41 is disposed betweenthe resin barrier 41 and the set of all units (Bmn). For the finalproduct, each unit display panel should be separated independently.Therefore, after cutting out the resin barrier 41, each unit displaypanel should be separated by cutting the flexible display device in aunit panel (Bmn).

For another example for pattern of resin barrier 41, as shown in FIG.5B, the resin barrier 41 is formed with a matrix shape to surround eachunit display panel (Bmn). In that case, the cutting line 45 is disposedbetween each unit display panel (Bmn) and the resin barrier 41. Bycutting the flexible display panel along the cutting line 45, the resinbarrier 41 is removed and the respective unit display panels areseparated.

As shown in FIG. 6 illustrating a second exemplary embodiment of thepresent invention, the flexible display panel includes a flexiblesubstrate 27, a display element layer 25 formed on the flexiblesubstrate 27 and an insulating protection layer 23 including a firstprotection layer 23 a and a second protection layer 23 b. The firstprotection layer 23 a includes the silicon layer or the metal oxidelayer. The second protection layer 23 b includes silicon nitride (SiNx)or silicon oxide (SiOx) having a better insulating property than thefirst protection layer 23 a. In the second exemplary embodiment of thepresent invention, except that the insulating protection layer 23includes the two layers, others are the same as in the first embodiment.

The method for manufacturing the flexible display device according tothe second exemplary embodiment of the present invention is differentfrom the first exemplary embodiment in the step of forming theinsulating protection layer 23. Except for forming the insulatingprotection layer 23 including the first protection layer 23 a and thesecond protection layer 23 b, the other steps are the same as in thefirst exemplary embodiment of the present invention. Therefore, the sameexplanation is not duplicated here. A silicon nitride (SiNx) or asilicon oxide (SiOx) is deposited on the glass substrate 21 by PECVDmethod to form the first protection layer 23 a. Then, in the same PECVDmethod, a silicon material is deposited on the first protection layer 23a continuously to form the second protection layer 23 b. Alternatively,a metal material may be deposited on the first protection layer 23 a andthe metal material may be oxidized by an O₂ plasma or an anodizingmethod to form the second protection layer 23 b. After that, by the samemethod explained in the first exemplary embodiment, the display element25 is formed, the flexible substrate is attached, and the glass (rigid)substrate is removed to complete the flexible display device as shown inFIG. 6.

FIG. 7 illustrates an exemplary display element layer 25 used for theflexible display device according to the present invention. FIG. 7 showsa TFT array layer as the display element layer 25 of a display devicesuch as an LCD display.

As shown in FIG. 7, the TFT 99 includes a gate electrode 132 connectingto a gate line 112, a source electrode 144 connecting to a data line122, a drain electrode 142 connecting to a pixel electrode 148, and asemiconductor layer 138 forming a channel between the source electrode144 and the drain electrode 142 and overlapping the gate electrode 132on a gate insulating layer 105. The semiconductor layer 138 includes anactive layer forming the channel overlapping the source electrode 144and the drain electrode 142, and an ohmic contact layer 136 for reducingthe contact resistance between the active layer and the source electrode144 or the drain electrode 142. The pixel electrode 148 is connected tothe drain electrode 142 of the TFT 99 through the pixel contact hole 151penetrating through a passivation layer 103. In response to the scansignal supplied through the gate line 112, the TFT 99 charges the videosignal supplied through the data line 122 to the pixel electrode 148.The array of the TFT 99 is formed by multiple photo-lithographyprocesses and etching processes.

As shown in the FIG. 7, the surface of the display device having TFTarray does not have a level surface due to the various overlappedpatterns. In the subsequent process for attaching the flexiblesubstrate, if the flexible substrate is attached on the uneven surfaceof the display element layer having the TFT array, the pressing forcefor attaching the flexible substrate is not evenly applied to thedisplay element layer. Therefore, the elements where the attaching forceis large may be easily broken. This causes the defect on the TFT 99performance or characteristics. To make the surface of the displayelement layer smooth, an overcoat layer 101 is deposited on the displayelement layer. The overcoat layer 101 makes the surface of displayelement layer having TFT 99 even leveled and acts as a buffer todisperse the pressure applied while attaching the flexible substrate.Further, the overcoat layer 101 can protect the TFT 99. The overcoatlayer 101 is formed by depositing at least one of a resin, a liquefiedsilicon nitride (SiNx) or a silicon oxide (SiOx) and curing it at acertain temperature. Further, mixing the overcoat layer 101 materialwith the adhesive used for attaching the flexible substrate, theleveling of the display element layer and the attaching the flexiblesubstrate can be conducted at the same time.

The first and second exemplary embodiments as described thus far use aglass substrate as the rigid substrate in the substrate transcriptionmethod. In the third exemplary embodiment of the present invention, thedisplay element layer is formed on a stainless steel (or SUS) substratewhich is cheaper than a glass substrate and easier to remove by theetching method. Herein, the flexible substrate is attached, and then,the rigid SUS substrate is removed by the etching method. Generally,iron chloride (FeCl₂) is used for etching the stainless steel substrate.Iron chloride can easily etch a ferrous material, such as stainlesssteel, but hardly etch the organic material. Therefore, in the thirdexemplary embodiment, a stainless steel substrate is used for the rigidsubstrate, and organic materials are used for the gate insulating layer,the passivation layer and the overcoat layer of the display elementlayer shown in the FIG. 7. An organic material is also used for theinsulating protection layer, and an organic material is used for theflexible substrate. Further, iron chloride is used as the etchant forremoving the rigid substrate.

FIG. 8A illustrates the first step of a manufacturing method accordingto the third exemplary embodiment. On a stainless steel substrate 61, aninsulating protection layer 63 is formed. The insulating protectionlayer 63 includes at least one of acrylic organic material, BCB (benzocyclobutene), PFBC (Perfluorocyclobutane), Teflon, Cytop and Polyimide.Then, as shown in FIG. 8B, a display element layer 65 is formed on theinsulating protection layer 63. At this time, when the TFT elements areformed as shown in FIG. 7, the gate insulating layer 105, thepassivation layer 103 and the overcoat layer 101 include any one ofacrylic organic material, BCB (benzo cyclobutene), PFBC(Perfluoro-cyclo-butane), Teflon, Cytop and Polyimide. Especially, atdepositing the overcoat layer 101, the side parts of the display elementlayer 65 should be fully covered by the overcoat layer 101 to protectefficiently. Next, as shown in FIG. 8C, a flexible substrate 67 isattached on the display element layer 65. The flexible substrateincludes organic material, such as plastic material. Finally, as shownin FIG. 8D, the whole substrate attaching the flexible substrate 67 isput into an etch bath 71 filled with the etchant 73 to remove thestainless steel substrate 61. The etchant 73 includes iron chloride(FeCl₂) or other suitable etchant or a combination of suitable etchants.At this time, the side portions of the display element layer 65 can beprotected from the etchant by the organic insulating layer, organicpassivation layer and organic overcoat layer. Further, the insulatingprotection layer 63 protects the display element layer 65 from theetchant while the stainless steel substrate 61 is entirely removed bythe etching process. After the etching process, the substrate is takenout of the etching bath 71 and cleaned of any remaining etchant, theflexible substrate is completed as shown in the FIG. 8E. When theflexible substrate comprises multiple unit display panel arrayed inmatrix type, the unit display panels are separated by a cutting process.

In accordance with exemplary embodiments of the present invention, theinsulating protection layer has the 1/20 or less of the etchingselectivity as compared to the rigid substrate so as not to be removedduring the etching process for removing the rigid substrate. Therefore,the display element can be protected from the etchant used for removingthe rigid substrate. As a result, the present invention ensures thestability in the manufacturing process of the flexible display device.Further, the present invention suggests a method for manufacturingprocess having increased production yield.

It will be apparent to those skilled in the art that variousmodifications and variations can be made in a method for manufacturingthe flexible display device and a flexible display device of the presentinvention without departing from the spirit or scope of the invention.Thus, it is intended that the present invention cover the modificationsand variations of this invention provided they come within the scope ofthe appended claims and their equivalents.

1. A flexible display device, comprising: a flexible substrate; adisplay element layer formed on the flexible substrate; an insulatingprotective layer covering the display element layer; and a rigidsubstrate having an etching selectivity at least 20 times greater thanthat of the insulating protective layer.
 2. The flexible display deviceaccording to the claim 1, wherein a thickness of the insulatingprotection layer is substantially 1 μm or less.
 3. The flexible displaydevice according to the claim 1, wherein the insulating protection layerincludes at least one of silicon, silicon nitride (SiNx), silicon oxide(SiOx), metal oxide, and organic material.
 4. The flexible displaydevice according to the claim 3, wherein the insulating protection layerincludes a metal oxide having at least one of chrome oxide(Cr_(x)O_(y)), tantalum oxide (Ta_(x)O_(y)) and aluminum oxide(Al_(x)O_(y)).
 5. The flexible display device according to the claim 3,wherein the insulating protection layer includes an organic materialhaving at least one of acrylic organic material, BCB (benzocyclobutene), PFBC (Perfluorocyclobutane), Teflon, Cytop and Polyimide.6. The flexible display device according to the claim 1, wherein theinsulating protection layer includes at least two layers.
 7. Theflexible display device according to the claim 1, wherein the rigidsubstrate is a glass substrate.
 8. The flexible display device accordingto the claim 1, wherein the rigid substrate is a stainless steelsubstrate.
 9. A manufacturing method for flexible display device,comprising the steps of: forming an insulating protection layer on afirst substrate; forming a display element layer on the insulatingprotection layer; attaching a flexible substrate on the display elementlayer; and etching the first substrate to remove the first substrateusing an etchant having a selective etching ratio of the insulatingprotection layer to the first substrate of less than 1/20.
 10. Themanufacturing method of a flexible display device according to the claim9, wherein the insulating protection layer has a thickness of 1 μm orless.
 11. The manufacturing method of a flexible display deviceaccording to the claim 9, wherein the step of forming the insulatingprotection includes depositing any one of a silicon layer, a siliconnitride layer, a silicon oxide layer, a metal oxide layer and an organiclayer on the first substrate.
 12. The manufacturing method of a flexibledisplay device according to the claim 9, wherein the metal oxide layerincludes at least one of chrome oxide (Cr_(x)O_(y)), tantalum oxide(Ta_(x)O_(y)) and Aluminum oxide (Al_(x)O_(y)).
 13. The manufacturingmethod of a flexible display device according to the claim 9, whereinthe organic layer includes at least one of an acrylic organic material,BCB (benzo cyclobutene), PFBC (Perfluorocyclobutane), Teflon, Cytop andPolyimide.
 14. The manufacturing method of a flexible display deviceaccording to the claim 9, wherein the insulating protection layer hastwo or more layers.
 15. The manufacturing method of a flexible displaydevice according to the claim 9, wherein the first substrate includes aglass substrate.
 16. The manufacturing method of a flexible displaydevice according to the claim 15, wherein the etching the firstsubstrate includes wet-etching the first substrate with an etchantincluding buttered hydrogen fluoride (HF+NH₄F:BHF).
 17. Themanufacturing method of a flexible display device according to the claim16, further comprising the steps of: before the step of etching thefirst substrate, forming a resin barrier on the first substrate on aside opposite to an insulating protection layer; and after the step ofetching the first substrate, removing the resin barrier.
 18. Themanufacturing method of a flexible display device according to the claim15, wherein the etching the first substrate includes dry-etching thefirst substrate with an etchant including any one of CF₄+O₂ and SF₆+O₂.19. The manufacturing method of a flexible display device according tothe claim 9, wherein the first substrate includes a stainless substrate.20. The manufacturing method of a flexible display device according tothe claim 19, wherein the step of etching the first substrate includeswet-etching the first substrate with an etchant including iron chloride(FeCl₂).